Apparatus for drying macaroni products



June 18, 1963 R. SAMSON 3,094,398

APPARATUS FOR DRYING MACARONI PRODUCTS Original Filed Oct. 24, 1956 WWW IIIIIJI HHHHHIIII FEM: 514/146 O/V United States Patent 3,094,238 APPARATUS FOR DRYING MACARONI PRODUCTS Rene Samson, Montreal, Quebec, Canada, assignor to Gisbruder Buhler, Uzwil, Switzerland, a firm of Switzer and Original application Oct. 24, 1956, Ser. No. 618,074. Divided and this application Nov. 2, 1960, Ser. No. 71,375 6 Claims. (Cl. 34-212) The present invention relates to improvements in the manufacture of alimentary paste products and more specifically to improvements in the drying operations necessary in manufacturing macaroni products of alimentary paste compositions The term macaroni products is intended to cover all varieties of many different shapes of alimentary pastep roducts, for example, long and short macaroni, spaghetti, vermicelli, noodles, alphabets, and the like.

It is extremely important in the manufacturing process of products of this nature that the finished product be stabilized to withstand handling for packaging, shipping or storage under varying conditions of temperature and humidity with a minim-um of breakage even after several days or weeks of storage. This desired result depends largely on the efieotive and controlled stabilization of the product during the drying operations.

The drying methods in common use at the present time, in attempting to achieve this desired stabilization necessitate considerable time in the drying and generally require difiicult processes and measures of control which are critical and expensive.

Broadly, the drying procedure involves two main steps, the first of which includes the preliminary drying of the alimentary paste product after it has been extruded into the desired shape from a press, and a resting period under definite and controlled conditions of humidity and temperature. It is in the preliminary stage of drying that the conversion of protein into gluten, already started during the kneading operations in the press, continues to take place at a faster rate.

The second main step includes a further stage of drying to complete the hydrolysis of protein into gluten followed by a final dehydration stage. Each of these steps and their intermediate stages must be carried out as mentioned above under controllable and definite conditions of temperature and relative humidity.

The most critical of the steps mentioned, with respect to satisfactory stabilization of the goods, is the second step where the hydrolysis must be completed. The quality of the finished products and the time required to carry out the drying process depends largely on this step, as long as preliminary drying operations have been carried out in the proper and right conditions of drying process.

'It has been proposed in the prior art that this step might be accelerated by soaking the extruded product in boiling water for a short period of time, drawing the water oil? and drying the product immediately afterwards at a high temperature. However, this has not been too satisfactory in that the resultant product is not stable and the shape of the product is altered and twisted. It should be mentioned that in addition to the stability required, it is very important that in the manufacturing of macaroni products the shape, as extruded, be maintained during the drying operations. Otherwise, the finished products will be difficult and in fact impractical for the necessary subsequent handling and packaging. To the best of the applicants knowledge, no satisfactory method has yet been proposed tor the carrying out of this important drying process in a manner which is efiicient, suitable for application in automatic dryers, and capable of yielding ice a satisfactory product with respect to the desired uniformity of shape, stability and quality.

The present application is a division of the applicants United States application Serial No. 618,074, filed October '24, 1956, now Patent No. 2,988,819, which is directed to a method of carrying out this critical drying step which is applicable to any and all types of drying apparatus and which will yield a product having the desired qualities mentioned.

Briefly, it has been found that a main factor controlling the efiectiveness and speed of the first and second critical drying steps consists in the breaking down of the surfiace tension of the water in and on the surface of the goods during the entire drying operation and particularly during the hydrolysis stage.

It should be explained that all varieties of macaroni products in the extruded or shaped condition from a press have a moisture content of from about 26% to about 34%. In the preliminary drying stage after extrusion, drying operation is rapid in order to eliminate the excess moisture on the surface of the goods and speed up the hydrolysis and conversion of protein into gluten. It is followed by the resting period to allow the moisture within the goods to equalize all through the mass of the product. In this resting period there is substantially no circulation of air. In this preliminary drying a very high hygroscopic condition with a very high relative humidity above must be maintained using air at temperatures varying between 70 F. to F. depending on the type of dryers used which will remove the excess moisture from the surface of the product. From this first step the products are brought to the second and most important step of this drying process after the percentage of moisture has been reduced down to from about 17% to 21%, in the macaroni products which means over 60% of the humidity to be removed from. the product.

In this step and after the moisture content of the prodnot has reached the required level from 17% to 21%, the exothermic reaction which must take place due to hydrolysis of protein into gluten is practically completed. This hydrolysis is not chemically a complete reaction, otherwise the gluten would not retain its elasticity as is necessary for stabilized product. Finally, the products are subjected to further drying stage reducing the moisture content to about 14% or less which means less than 40% of the total moisture to be removed from the product.

As is well known in the art, one of the main difiiculties in the drying of macaroni products is that they are non-conductive, thus creating a problem in removing the water evenly and equally from the interior to the exterior of the product. Accordingly, when prior art attempts have been made to achieve the desired acceleration of this important drying process described and the resulting hydrolysis the main idea has been to subject the goods in this second stage to increased temperatures which unfortunately prevented a thorough stabilization of the product and also served to unequally dehydrate the product and set up contraction or stresses which cause the product to break or crack. This latter phenomenon is known in the trade as checking.

In accordance with the method of application Serial No. 618,074 the hydrolysis action of the second step can be accelerated and completed by recirculating air through the products which has already passed through the products and therefore contains a percentage of organic matter. It has been found that this "old or organic matter containing air has a somewhat catalytic action breaking up and reducing the surface tension of water in and on the products. By the reduction of surface tension the removal of moisture from the products is greatly accelerated which permits the drying operations a to be carried out at a relatively low temperature and at the same time speeds up the hydrolysis or conversion of protein to gluten in such a way so as to stabilize the products prior to the final reduction of moisture content to the level required when the products come out of the dryer.

Since over 60% of the moisture is removed from the product in the preliminary stage, it is very important and even necessary for maximum results to re-use and recirculate substantially all the air used in the preliminary stage into the second drying stage because this air contains the highest percentage of volatile constituents of organic matter from the drying products.

More specifically, and in accordance with the present method, to obtain maximum results, from 80% to a preferred 100% of the air circulated in the dryer units is old or organic matter bearing air. If percentages as low as 60% to 40% or even 20% are made use of, the drying process requires higher temperature and longer drying time proportionate to the decreasing percentage of recirculated conditioned air used in the process. This air is preferably produced in the dryer by the operational functions of the dryer and is preferably used in all stages of the drying operations.

For example, in an automatic dryer of the type having a first or preliminary stage unit and a single second stage or multiple intnerconnected second stage units, the air is Withdrawn from the front of the second stage units and recirculated back in the first stage unit or preliminary.

It is then circulated through the first stage unit or preliminary and back to the last end of the second stage units where the dried goods are coming out and through all the second stage units back to the front unit of the second stage from there, back intopreliminary and so on in a closed circuit. Since in a modern type automatic dryer, the distance from the first stage unit to the last of the second stage units is considerable, about 100 feet or more, when the old air is recirculated through an outside duct it is cooled down from about 115 F. as it leaves the first stage unit, to about 65 F. or substantially room temperature as it re-enters the last of the second stage units. This makes it possible to control the moisture content of the recirculated air directly since if the moisture content of the air becomes too high it will condense partially within the latter portion of the duct and this condensate can be easily removed. If the moisture content is too low, it can be increased by an injection of steam or water spray. If necessary a small percentage of fresh air can be introduced to achieve the desired balance of humidity and temperature. Since the organic matter carried in the air is more volatile than water, it will not condense at the same rate and will thus be carried back into the dryer even if a fairly large percentage of moisture in the circulated air is eliminated as a condensated product.

The advantages arrived at by this method are many and principally that macaroni products thus produced have a uniform shape, excellent colour and texture as Well as quality and are completely stable as required for efficient handling and packaging. Since they are dried at relatively lower temperatures and in a shorter period of time than was possible by the prior art methods known the saving in manufacturing costs is considerable.

In order to illustrate diagrammatically one preferred way of carrying out the method of application Serial No. 618,074 in an automatic continuous flow dryer set-up reference will be made to the accompanying drawing where represents a first stage or preliminary dryer unit through which the macaroni products pass in the first relative rapid drying and-resting period which is intended to reduce the moisture contents of the goods down from about the usual 26% to 35% as they come out of the presses to about as they proceed to the second drying 4 stage. The second stage dryer unit indicated at 12 may consist of a single tunnel or any uneven number of courses or interconnected casings depending on the temperatures and the type of air circulating device utilized. During each course the goods are conveyed along a circuitous path and subjected to alternate periods or zones of drying and resting so as to equalize the moisture removal. The drying temperatures are reduced from one course to the next to avoid a too high surface dehydration of the products as their moisture content diminishes.

It should be mentioned that long goods are usually dried in installations of this nature While short goods are usually dried on moving screens in layers of different thickness. The term long goods in the art refers to macaroni products having a length of from about 6 inches or longer. The term short goods is usually applied to lengths of less than 6 inches such as, alphabets, twisted noodles, elbows or the like. It will be appreciated that while the present method is fully eifective in the drying of short goods it is directed mainly to the drying of long goods which as previously explained are considerably more diflicult to handle and require a longer time to dry than short goods.

In the type of automatic dryer unit diagrammatically illustrated conveyor means are provided for conveying the product A through the various drying stages and each unit is provided with controlling means to regulate the temperature and humidity of the air within the units. Ordinarily and using the known standard drying methods, the first unit 10 which removes the major portion of the surface moisture is maintained at from about 150 F. to about 180 F. and the second stage units are maintained at from about 140 F. at the first course down to about 75 F. and sometimes over F. at the last course. In some types of automatic dryers a cooling stage separated from the dryer itself is required.

With the present apparatus the temperature of the first unit 10 can be reduced to about F. and the second unit from about 90 F. at one end to about 65 F. at the other end, while the drying time can also be considerably reduced.

To efiiciently carry out the method of application Serial No. 618,074 in the apparatus shown, and by way of illustration, a first conduit or duct 14 is provided which connects the second stage casing 12 to the first stage unit so that air is drawn from the unit 12 adjacent the first course and delivered to the upper portion of the unit 10. A valve or damper 18 is also provided whereby the duct 14 can be closed off. If a small percentage of fresh air is required, valve 23 can be opened. A heater 30 can be made use of to increase temperature of the air.

A second and elongated duct 20 extends from the front and upper portion of the second unit 12 to the last course or end of the combined units 12 so that the air when circulated through the unit 12 against the conveying course of the goods is recirculated back to the first stage of the drying operation, by means of fan 36 through duct 14. This air passes through the unit I10 and is again withdrawn by the duct 8 forming a substantially closed circuit. A fan or blower 16 is connected into the duct 20 to cause a circulating air stream. Fan 16 is placed at front end of second stage to permit recirculation of air from front to back end of unit 12 when preliminary dryer is closed down, for example when the extruding or forming press 'is stopped and dryer is being emptied for shut down.

A further duct 22 is provided on the first stage unit 10 and serves to draw the air through the duct 8 from the bottom of the unit and recirculate it through the top of the unit thus forming a separate closed circuit for the first or preliminary drying stage. A valve or damper 26 is provided so that the duct 22 can be closed off in normal operation.

Y The reason for the separate circuit created by the duct 22 is that in starting up the dryer, and in order to provide the required old or organic matter bearing air, the first stage unit is operated as a closed circuit until the goods have passed through the preliminary drying and resting. For this purpose the duct 14 is closed ofi and the duct 22 opened, duct 8 is also closed from the duct 2&1" with damper 38 so that the drying air within the unit is recirculated by the fan or blower 39 through the goods and becomes old or organic matter bearing. Once the goods are ready to pass into the second drying stage the duct 22 is closed ofi, damper 38 is opened and the duct 14 opened so that the organic matter bearing air is recirculated through the entire second stage unit and is now Withdrawn from the second stage by the duct 14 and recirculated back through the first unit 10. Air from unit it is drawn back into 12 by fan 16 through duct 8.

As previously mentioned, since the duct 20' is an ex terior duct and of a considerable length, in the order of 100 feet long, the air passing along the duct is cooled say from about 115 R, which is the operating temperature of the first unit 16 under the conditions of the present method, down to about 65 F. or approximately [room temperature at the far end as it enters the unit 12. This heat exchange or cooling efiect makes it possible to maintain the interior temperatures of the units 16, 12 at the desired controlled degree without the necessity of providing additional temperature and humidity controls beyond those generally required in apparatus of this nature. If the recirculated air becomes too wet and condensation occurs in the cooling along the duct 20 it is a simple matter to provide a condensate trap or the like. If the humidity rises beyond a required predetermined degree, a small percentage of fresh air can be introduced from a controlling point 41 controlled by a damper 42 and connected into the duct 20. It is preferable, however, not to draw fresh air into the duct. Cooling the air in the duct with a refrigerating device of some kind is more desirable so as to maintain the highest pos sible percentage of organic matter in the air.

If it is necessary to raise the humidity of the recirculating air, steam or a water jet can be injected at the control point. Since these expedients are well known in the art and do not form part of the invention, it is not thought necessary to describe or illustrate them in detail. On duct 20 a trap 32 is provided to let a percentage of air out of the duct if the pressure is too high. The trap door 32 is controlled by a weight equivalent to pressure required to open it.

With automatic dryers known controlling apparatus can be made use of in any stage of the drying process of the invention to control the air circulation, its volume, speed, temperature, relative humidity, volume of recirculated air, as well as its percentage of organic matter, in-

take of fresh air. In this way a drying apparatus adapted to carry out the invention can be made fully automatic to compensate for and control in all respects the different factors involved in the drying process whether it involves single or multiple drying stages.

I claim:

1. In a dryer apparatus for alimentary paste products, comprising a preliminary dryer unit and a finishing dryer, an air duct connecting the entrance part of said finishing dryer with the said preliminary dryer unit, a long duct disposed externally of and connecting the preliminary dryer unit and the end part of said finishing dryer, a third duct closely connected between said air duct and said long duct for the purpose of selectively establishing a closed circuit for said preliminary dryer unit, the moisture laden drying air being cooled by thermal losses in said long duct, heating means for the air used in said preliminary dryer unit, and blower means for displacing the drying air through said ducts, said preliminary dryer and said finishing dryer.

2. In a dryer apparatus according to claim 1, said long duct being provided with an adjustable air inlet for fresh air.

3. In a dryer apparatus according to claim. 1, said long duct being provided with an adjustable outlet to the atmosphere.

4. -In a dryer apparatus for alimentary paste products comprising a preliminary dryer unit and a finishing dryer, an air duct connecting the entrance part of said finishing dryer with the said preliminary dryer unit, a long duct disposed externally of and connecting the preliminary dryer and the end part of said finishing dryer, a third duct closely connected between said air duct and said long duct for the purpose of establishing a closed circuit in the finishing dryer for static drying when required, the moisture-laden drying air being cooled by thermal losses in said long duct, heating means for the air used in said preliminary dryer unit, and blower means for displacing the drying air through said ducts, said preliminary dryer and said finishing dryer.

5. In a dryer apparatus according to claim 4, said long duct being provided with an adjustable air inlet for fresh air. l

6. In a dryer apparatus according to claim 4, said long duct being provided with an adjustable outlet to the atmosphere. l l i ltil Puccinelli Feb. 15, 1949 Giroud Apr. 30, 1957 

2. IN A DRYER APPARATUS FOR ALIMENTARY PASTE PRODUCTS, COMPRISING A PRELIMINARY DRYER UNIT AND A FINISHING DRYER, AN AIR DUCT CONNECTING THE ENTRANCE PART OF SAID FINISHING DRYER WITH THE SAID PRELIMINARY DRYER UNIT, ALONG DUCT DISPOSED EXTERNALLY OF AND CONNECTING THE PRELIMINARY DRYER UNIT AND THE END PART OF SAID FINISHING DRYER, A THIRD DUCT CLOSELY CONNECTED BETWEEN SAID AIR DUCT AND SAID LONG DUCT FOR THE PURPOSE OF SELECTIVELY ESTABLISHING A CLOSED CIRCUIT FOR SAID PRELIMINARY DRYER UNIT, THE MOISTURE LADEN DRYING AIR BEING COOLED BY THERMAL LOSSES IN SAID LONG DUCT, HEATING MEANS FOR THE AIR USED IN SAID PRELIMINARY DRYER UNIT, AND BLOWER MEANS FOR DISPLACING 